JPH0455251B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Field of Industrial Application The present invention relates to a mass flowmeter that utilizes the Coriolis force.

2. Prior Art When vibration is applied to a fluid flow flowing through a flow tube, Coriolis force is generated in a direction perpendicular to the direction of the fluid flow and the vibration axis of the flow tube, and this Coriolis force is caused by vibration frequency. It is known that this is proportional to the mass flow rate of the fluid, and a mass flow meter using the Coriolis force is disclosed in Japanese Patent Application Laid-Open No. 54-52570. This conventional example has a body shape in which a U-shaped conduit having an inlet and an outlet portion is fixed to a support member, and fluid flows out from the inlet portion through the U-shaped conduit. Rotate the U-shaped conduit in a direction perpendicular to the U-shaped conduit surface (the surface on which the conduit is made) around the support fixing line (the line connecting the support where the inlet and outlet are supported). When applied, a Coriolis force acts on the fluid flowing through the U-shaped conduit, producing torsional vibrations proportional to the Coriolis force about the U-tube axis perpendicular to the anchor line. This Coriolis force is determined from the time difference when the conduit passes through the reference plane.

3 Problems to be Solved by the Invention In the conventional example described above, the Coriolis force is detected as the amount of twist of the U-shaped conduit, but the U-shaped conduit is subjected to vertical vibrations on the conduit surface. However, since the conduit surface is installed horizontally or parallel to the pipe, it is easy to react to disturbances such as floor vibration in the former case and lateral vibration of the pipe in the latter case, and also has high sensitivity. Since a thin-walled pipe is used for detection, its rigidity is low, which also makes it susceptible to external disturbances, making it difficult to perform detection with a high S/N ratio.

4. Means for solving the problem The present invention has been made in order to solve the above-mentioned problems. That is, by arranging the conduit surface perpendicular to the piping, the rigidity of the conduit in the lateral direction, which is susceptible to the effects of piping vibration, is increased.

5 Embodiments FIG. 1 is an explanatory diagram of the present invention, where A is a plan view, B is a side view, and C is a front view. , a conduit 2 communicates between the upstream and downstream sides of the split.
As shown in Figures A, B, and C, the conduit 2 has a loop shape that surrounds the flow tube 1 on substantially the same plane, and the inlet 21 and outlet 22 are formed on the flow tube wall. The opening is symmetrically located with respect to the first axis indicated by XX' on the diameter. In addition, the conduit A and B sections near the inlet 21 and the outlet 22 are approximately parallel to the first axis, and the conduit 2 can rotate around the first axis using the inlet 21 and the outlet 22 as fulcrums. It's summery. Further, the line YY' connecting the inlet 21 and the outlet 22 is a second axis, and the conduit 2 is symmetrical with respect to the second axis and the first axis, except for the above-mentioned portions A and B. The fulcrum 7 pivots the conduit 2 to the flow tube 1 in a oscillatory manner as required.

A non-magnetic ring 35 is fixed to a position on the second axis of the loop constituting the conduit 2, and a magnet 3 is attached to the ring 35.
is fixed. The magnet 3 repeatedly attracts and repels the magnet 3 when a coil 4 attached to a support 5 fixed on the flow tube is excited by the natural frequency AC power source (not shown) of the conduit. This situation is shown by dotted lines in Figures 3-1 and 3-2.

The fluid flows in through the inlet 21, flows through the conduit 2 in a loop as shown by the arrow, and flows out through the outlet 22 downstream of the dividing plate 6. If the vibration of conduit 2 is in the direction of the right-hand screw facing in the Coriolis force is generated from the paper surface to the front side in the section. The magnitude of this force is proportional to the fluid mass flow rate for a constant vibration frequency. In addition, if the vibration is in the direction of the right-hand screw facing in the X direction (i.e., in the case of the dotted line in Figure 3-1),
Coriolis force is applied in the opposite direction to that described above. This means that an alternating displacement as shown by the dotted lines in FIGS. 2-1 and 2-2 occurs, and as this is added to the drive vibration, the conduit is rotationally displaced around the second axis. This rotational displacement is measured by detectors m, n, not shown,
Alternatively, the mass flow rate can be determined by disposing it at M and N and measuring the rotational displacement, which is the Coriolis force, at the time it takes to pass through a reference surface such as a stationary surface of the conduit loop.
Further, at A and B near the inlet 21 and the outlet 22, the amount of twist around the second axis can be detected using a strain gauge or the like on the front and back sides of the paper of A and B.

FIG. 2 shows another embodiment of the present invention. The conduit 2 in the embodiment shown in FIG. A magnet 3 fixed to a non-magnetic ring 35 is attached to a position on two axes, and a coil 4 is attached to a position corresponding to the magnet 3 of the second conduit 30. By repeatedly attracting and repelling the magnet 3 using an AC power source (not shown) with a frequency substantially equal to the natural frequency, each of the first and second conduits is excited around the first axis in opposite phases. be done. Naturally, at the point of symmetry between the magnet 3 and the coil 4, which are the excitation means, with respect to the first axis, they are separated when the excitation means is attraction. The opposite case also holds true. Looking at the generation of Coriolis force in the case of repulsion on the excitation means side, in conduit 2, the first
As in Figure C, M, direction toward the paper on the m side, N,
On the n side, the direction approaches from the plane of the paper, and in the conduit 30, the rotation around the first axis is in the X direction, which is opposite to the movement of the conduit 2. That is, the movement moves in the direction of approaching on the m side and moving away on the n side, and in the next half cycle, on the contrary, the m side moves away and the n side approaches. In this case as well, the Coriolis force passes through the reference plane m,
It is detected as a time difference from a signal by a "position" or "velocity detection" means (not shown) installed near point n. Note that in order to impart accurate harmonic vibration to the conduit loop, a fulcrum 7 that rotatably supports the conduit section on the XX' axis may be supported on the flow tube 1.

6. Effects As explained above, according to the present invention, the surface of the conduit loop is perpendicular to the pipe, so that the conduit loop can withstand lateral vibrations that occur due to the low rigidity of the pipe. The planes of are parallel,
The least vibrational influence is obtained for the signal direction of the Coriolis force detected in the direction perpendicular to the conduit loop.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, in which A is a plan view, B is a side view, and C is a front view. FIG. 2 shows another embodiment. In the figure, 1 is a flow tube, 2 and 30 are conduits, 3 is a magnet,
4 represents a coil, and 6 represents a dividing plate.

Claims (1)

[Scope of Claims] 1. A conduit comprising a conduit that flows in from the upstream side obtained by dividing the flow of the flow tube with a dividing means, surrounds the flow tube in a loop shape, and flows out to the downstream side of the dividing means, and The conduit is placed substantially on the same plane as the flow tube cross section, and the positions of the inlet and outlet of the conduit on the flow tube wall are arranged symmetrically and close to each other with respect to a first axis when the flow tube diameter is the axis. At the same time, predetermined sections of the conduits near the inlet and outlet are made substantially parallel to each other, and the conduits are formed into a loop that is symmetrical with respect to a first axis and symmetrical with respect to a second axis that connects the inlet and outlet. death,
A mass characterized in that an excitation means that performs harmonic motion about a first axis is provided, a detection means is provided for detecting a Coriolis force generated around a second axis, and a mass flow rate is measured by the Coriolis force. Flowmeter. 2. The loop-shaped conduit described above has a first conduit and a second conduit of the same shape and size as the first conduit, which are arranged with a slight distance in the axial direction of the flow tube, and the first conduit and the second conduit are
2. The mass flowmeter according to claim 1, further comprising a vibrating means for vibrating the conduit in a phase opposite to that of the conduit.